Total Phosphorus (TP) criteria have been established for 13 segments of Lake Champlain in the Vermont Water Quality Standards and in a New York, Quebec, and Vermont Water Quality Agreement for Lake Champlain. TP criteria were developed to protect recreational uses and enjoyment of the lake, in part, through an analysis of lake user survey data, paired with monitoring data for TP, chorophyll a, and Secchi depth. The user surveys used qualitative assessment endpoints such as clarity, algal greenness, foul odors, fish kills, and overall aesthetic enjoyment along with corresponding measurements of lake phosphorus levels to determine where to set numeric phosphorus criteria.

Researchers established a quantitative relationship between TP concentrations and the frequency of aesthetic problems and recreational use impairments caused by algae. Nuisance levels of algae were found to occur when TP concentrations reached 25 µg/L (instantaneous). TP criteria ranging from 10 to 25 µg/L were developed for the lake. The criteria were used to guide a process involving phosphorus load measurements and mass balance modeling that resulted in a phosphorus reduction agreement and basin plan completed in accordance with the federal Lake Champlain Special Designation Act of 1990.

Acceptable phosphorus loads were established for each subwatershed in Vermont, New York, and Quebec to meet the in-lake phosphorus criteria. The loading targets and a 20-year implementation timetable were incorporated into a comprehensive plan for the Lake Champlain Basin prepared by the Lake Champlain Management Conference. The phosphorus criteria for Lake Champlain were an important part of the overall phosphorus management goals for the lake and provided the basis for a phosphorus reduction agreement (USEPA 2000a).

Reference:

USEPA. 2000a. Nutrient Criteria Technical Guidance Manual: Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental Protection Agency, Office of Water, Office of Science and Technology, Washington, DC. Accessed October 2016. https://nepis.epa.gov/Exe/ZyPDF.cgi/20003COV.PDF?Dockey=20003COV.PDF.

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